Both patients with schizophrenia and patients with frontal lobe lesions have been described as deficient in suppressing irrelevant information. Recent findings, suggest that both patient groups may be capable of inhibiting distracting information when the stimuli are immediate, but exhibit impairments in sustaining inhibition over time. The sustainment of information across time require not only the maintenance of a memory trace, but the suppression of competing stimuli. As many parallels have been suggested in the literature between frontal lobe pathology and schizophrenia, it is critical to understand the links between symptomatology and cognitive behavior within these patient groups. This project proposes to investigate the temporal parameters of selective inhibitory processes in both patients with schizophrenia and patients with lesions to the prefrontal cortex. By the use of rigorous patient diagnostic screening, symptom assessment, clinical neuropsychological tests and computerized reaction time measures of inhibitory processes, the time course of inhibition in these two patient groups can be analyzed. Several experiments (see section 29.B) investigate: 1) the sustainment of inhibition at several inter-trial intervals; 2) the correlation between sequential inhibitory processes and clinical symptomatology; and 3) the sequential processing of relevant and irrelevant information. The comparison of the patterns of inhibitory deficits in neurological patients and patients with schizophrenia will elucidate the contribution of the prefrontal cortex in maintaining inhibition across time.